22nd November 2017
Recording the ashscape
This veteran ash tree, with its beautiful heart-shaped form created by cambium curving round the decayed hollow, can be found towards the bottom of a chalk downland valley in North Dorset.
With its hollow trunk, deadwood in the crown, rot holes and cavities, the tree has many veteran features and is hugely valuable for its biodiversity as well as its aesthetic appeal. It supports many species of lichens and bryophytes, some of which are almost entirely dependent on veteran ash trees, due to the unique characteristics of the bark. These include the (UK) priority lichen Bacidia incompta, and the nationally scarce Bacidia delicata and Caloplaca ulcerosa. The white-rot wood decay in the trunk provides decaying woody habitat for a range of saproxylic invertebrate species.
The effect of Chalara dieback of ash (Hymenoscyphus fraxineus) on open-grown trees like this ash was one of the subjects of discussion at the Ancient Tree Forum’s Autumn field event at Lyscombe Farm, which is within the Lyscombe and Highdon Site of Special Scientific Interest. Many of the older trees on the site are showing signs of dieback, but the impact so far appears to be much greater on some of the younger trees, particularly those which have been coppiced in recent years.
The impact of dieback on this area of Dorset and elsewhere in the country where ash trees are prevalent, could potentially be devastating, but in line with best practice, the veteran trees at Lyscombe are being left standing for as long as possible. Some ash trees appear to be more susceptible than others, but even if those infected die as a result of the disease, this could take many years, and the trees will remain valuable due to their scarcity and high habitat value even following their death. They are also a potential source of resilient material for the breeding of a new generation of Chalara -resistant ash.
Those attending the ATF’s event were urged to record all ash trees which have a diameter of 1.5 metres or above, to the Ancient Tree Hunt inventory (www.ancient-tree-hunt.org.uk), so that there will be a record in the future of which trees have survived Chalara and which haven’t.
The Ancient Tree Forum produced a position statement on managing the threat to ancient and veteran ash trees from Chalara in 2014 which can be downloaded from their website.
The ATF’s field event took place during a week-long ‘Ashscape’ event which was held at the Springhead Trust in North Dorset.